Weinhofer, I., Hehenberger, E., Roszak, P., Hennig, L., & Köhler, C. (2010). H3K27me3
Profiling of the Endosperm Implies Exclusion of Polycomb Group Protein Targeting by DNA Methylation.
PLoS Genetics, 6(10): e1001152. doi:10.1371/journal.pgen.1001152.